FOREST SERVICE. 541 



material tested green. This series will conclude the tests on impor- 

 tant structural woods of the Pacific Northwest. 



Tests were made on standard 6-foot, G-pin cross arms, divided 

 into seven groups, as follows: Douglas fir; shortleaf pine, natural 

 and creosoted ; longleaf pine, 50, 75, and 100 per cent heart ; and 

 southern white cedar. Users of cross arms have been demanding the 

 better grades and stronger kinds of timber. The tests indicate that 

 for arms of the dimensions of those tested less consideration need be 

 given to initial strength, and therefore a greater latitude can be 

 exercised in the choice of woods. 



The heavy loss incurred through damage to freight in transit has 

 turned the attention of railways and shippers to the better construc- 

 tion of wooden containers. Tests of nailed, wire-bound, and dove- 

 tailed packing boxes were undertaken in cooperation with the bureau 

 for the safe transportation of explosives and other dangerous articles. 

 The results of the tests were especially favorable to the wire-bound 

 boxes. A practical effect of the tests has been the modification of 

 regulations of the Interstate Commerce Commission and of specifica- 

 tions of the Navy Department in regard to boxes used for the trans- 

 portation of explosives. 



Throughout the Rocl^ Mountain region of Wyoming, Montana, 

 and Colorado western red cedar, imported from Idaho, has been the 

 chief wood used for poles. These three States, however, contain 

 much fire-killed lodgepole pine and Engelmann spruce. To secure 

 data on which a comparison of strength might be based, tests were 

 made on the Idaho cedar and on the Ilocky Mountain woods. Most 

 of these were completed the previous year, but the work was ex- 

 tended to include air-seasoned lodgepole pine poles cut from green 

 material. The results of the tests show that both the spruce and 

 pine, when properly treated with preservatives, are suitable for 

 poles. Their use for this purpose will lessen the cost of constructing 

 telejjhone lines throughout a wide region. 



The effect of preservative treatments on the strength of timber has 

 never been fully determined. Strength tests of stringers treated 

 with creosote by commercial processes have been in progress several 

 years. When the tests on Douglas fir, treated by the boiling process, 

 showed a decided weakening of the timber, it was thought probable 

 that the strength would be restored by seasoning. This, however, 

 did not prove to be the case. Air-seasoned (treated) stringers 

 showed a strength very little above that of the treated stringers tested 

 without seasoning. Small specimens will be treated and tested to 

 determine what part of the treating process is responsible for the 

 loss of strength, whether other species treated by the same process 

 show the same loss, and whether Douglas fir treated with creosote 

 by other processes is affected similarly to that treated by the boiling 

 process. 



PHYSICAL PROPERTIES AND STRUCTURE OF WOOD. 



In connection with the study of structural qualities of the various 

 woods, described in my last report, more than G50 permanent micro- 

 scopic slides, representing 100 different species, were prepared dur- 

 ing the year. A special study of the occurrence and significance of 

 tyloses in wood was completed, and shows that these have an impor- 

 tant bearing upon the absorption of preservatives. 



